Cloud top pressure. What does it mean to climate? The aerosol forcing corresponding to the ... the correlation of aerosol AOT and properties to cloud cover & height ...
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Kaufman, Koren, Remer, Rosenfeld & Martins
Koren, I., Y. J. Kaufman L. A. Remer and J.V. Martins, Measurement of the effect of Amazon smoke on inhibition of cloud formation, Science, 303, 1342-1344, 2004. http://climate.gsfc.nasa.gov/publications/fulltext/Koren_et_al._(2004).pdf
Cloud fraction as function of aerosol optical depth (OD). The cloud fraction decreases almost linearly with increasing OD.
• smoke instantaneous forcing -28w/m2 --> +8w/m2
• smoke 24hrs forcing -11w/m2 --> -5w/m2
• less radiation at the surface => less evaporation
• smaller boundary layer cloud fraction
The Atlantic Ocean - several aerosol types interacting with clouds June-Aug 2002
Stratus and trade cumulus
Cloud top pressure
Cloud top pressure
The aerosol forcing corresponding to the increase in cloud cover is ~ 6w/m2 in the June-Aug period over the Atlantic Ocean
We see similar increases in other locations, depending on the aerosol content of black carbon.
How does it reconcile with global warming?
x. What is the response of the cloud water path to 50 yr increase in aerosol concentration?
A. Fixed ocean temperature
B. feedback through ocean temperature
Takemura, Kaufman, Remer, Nakajima, submitted
• MODIS is in unique position to measure the correlation of aerosol AOT and properties to cloud cover & height
• We find increases in cloud cover on average of 0.05 → ~ 6 W/m2
• We find an average increase in cloud height of ~ 400 m (-40 mb)
• Model shows that long term aerosol cooling of the ocean may compensate the aerosol effect on cloud cover through impact on cloud microphysics